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Possible new meteor shower detected from CMN and SonotaCo data 4,5 ˇ ˇ Denis Vida1,2 , Filip Novoselnik1,2 , Zeljko Andrei´ c3 , Damir Segon , Korado 5 6 7 4 Korlevi´ c , Filip Matijevi´ c , Dˇ zan Jaˇ sarevi´ c , Anton Perkov , and Ciobanu Tudor8 1
Astronomical Society “Anonymus”, B. Radi´ ca 34, HR-31550 Valpovo, Croatia
[email protected] and
[email protected] 2
Faculty of Electrical Engineering, University of Osijek, Kneza Trpimira 2B, HR-31000 Osijek, Croatia
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University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering, Pierottijeva 6, HR-10000 Zagreb, Croatia
[email protected]
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Astronomical Society Istra Pula, Park Monte Zaro 2, HR-52100 Pula, Croatia
[email protected] and
[email protected]
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Viˇ snjan Science and Education Center, Istarska 5, HR-51463 Viˇ snjan, Croatia
[email protected] 6
Vladimir Prelog Science School, Vukovarska 269, HR-10000 Zagreb, Croatia
[email protected] 7
Astronomical Society “Orion” Sarajevo, Marˇ sala Tita 12, BIH-71000 Sarajevo, Bosnia and Herzegovina
[email protected] 8
International Computer High School of Bucharest, Mihai Bravu Street No. 428, Sector 3, RO-030328 Bucharest, Romania tudor
[email protected] The Croatian Meteor Network was started in 2007, and, since then, 19 055 orbits were obtained. A new meteor shower was detected using CMN and SonotaCo data. Basic orbital and activity data of this shower are described and discussed.
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Introduction
Early 2012, the Croation Meteor Network (CMN) was able to overcome a major obstacle. Software was developed for time synchronization between different stations. Before, the absence of such software prevented the calculation of high-precision orbits. Four years worth of data (2007–2010) were processed using the new software. For this period, 19 055 orbits have been acquired. It was decided to start searching for hitherto unknown meteoroid streams. The methods used and the first results are presented and discussed in this paper.
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white images at standard 25 frames per second, which allows for simple coupling with a PC: almost any framegrabber PC card or PC-TV card works with this camera. Readily available 4 mm f /1.2 objective lenses are used on most cameras. They provide a good compromise between sensitivity (the faintest meteors recorded with this objective are around magnitude +3.5) and image scale (which in this case is around 10′ per pixel). The image reduction procedure is described in detail by Vida and Novoselnik (2011).
Croatian Meteor Network
The CMN was started in 2007 by a group of enthusiasts ˇ led by Damir Segon. Since then, the CMN has grown into a large video meteor network with currently over 30 ˇ operational cameras (Andrei´c and Segon, 2010; Andrei´c et al., 2010). The entire airspace over Croatia is currently covered by at least two cameras (Figure 1). The network uses 1004× surveillance cameras for night-sky imaging. They are build around a Sony 1/3′′ EXView HAD CCD chip, and achieve a sensitivity of 3 mLux with an f /1.2 objective lens. They provide black and Figure 1 – Sky coverage at 100 km height at the end of 2011.
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Finding unknown meteoroid streams
We first combined our data sets with those of SonotaCo1 . After that, meteors belonging to known showers were excluded and the remaining meteors were plotted on a map of the sky. During plotting, the geocentric velocities of individual meteors were color-coded. Each day (solar longitude) had its own plot. These sky maps where visually searched for groups of dots of the same color. The exact position on the sky map and the range of solar longitudes were marked. After that, the data were run through our software called SelectedRangeFilter, which extracts orbital elements of meteoroids within the parameter range defined. The next step was to find the correlation of each meteoroid to every other meteoroid in this reduced data set. For that purpose, pyStreamFinder was used. This soft- Figure 2 – Right ascension/declination plot with color-coded ware compared each meteoroid to all other meteoroids geocentric velocity of the new stream. to find orbital similarities using the D-criterion. We required the value of DSH to be lower than 0.15. The literature describes different versions of the D-criterion method, but we implemented the original one (Southworth and Hawkins, 1963).
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Results
After filtering out Antihelion and other known sources, we were left with several potential candidates for the new streams. Among them, we have chosen the most promising one to be studied first, and the results of this study are presented in this paper. A total of 23 orbits (13 CMN and 10 SonotaCo) are possibly belonging to the new stream. The shower is active from λ⊙ = 145◦ to λ⊙ = 153◦ . Mean orbital Figure 3 – Orbits of the new stream. elements are given in Table 1. One can notice that they are similar to those of the Southern δ Aquariids (SDA) meteoroid stream, especially in eccentricity, perihelion δ Aquariid activity was detected from λ⊙ = 119◦ to distance, and geocentric velocity. λ⊙ = 144◦. Mean orbital elements for this stream obtained from the orbits obtained are also given in Table 1. The consistency of velocities can be seen in Figure 2. All velocities are in the range from 33 to 41 km/s. The radiants span from α = 355◦ to α = 365◦ in right as- 4.2 Comparison of the new stream and cension and from δ = −04◦ to δ = −10◦ in declination. SDA Orbits are quite consistent, too, and close to each other, The duration of the Southern δ Aquariid meteor shower as can be seen in Figure 3. covers the period from July 12 to August 19. They are shown in Figure 4 as gray orbits. The first meteors from our new shower appear on August 20 and last until 4.1 Southern δ Aquariids September 8. The new stream is plotted in black on After completing the data reduction process including Figure 4. At first sight, some correlation seems to exist detection, astrometry, and photometry, the results were between both streams. The new stream appears to be a stored in a .csv file with all data required for orbit anal- continuation of the Southern δ Aquariids, with similar ysis. A total of 268 Southern δ Aquariid (SDA) orbits (but not equal) orbital parameters. were found in the combined dataset for the 2007–2009 To investigate further the reality of this apparent correperiod. UFOOrbit software of SonotaCo was used for lation, the right ascension/declination plot is shown in orbit visualization and analysis. (UFOOrbit settings Figure 5. Southern δ Aquariid radiants are plotted in were: Q1, Gm = 2, dV = 15, GD > 10). Southern gray. They range from α = 332◦ to α = 355◦ in right 1 Simultaneously observed meteor data sets SNM2007, ascension and from δ = −22◦ to δ = −10◦ in declination. At the end of the Southern δ Aquariids’ activity SNM2008, and SNM2009; http://sonotaco.jp/doc/SNM/.
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Table 1 – Mean orbital elements of the new stream compared to those of the Southern δ Aquariids (SDA).
Stream New stream S δ Aquariids
α 0 ◦. 4 341 ◦. 9
δ −06 ◦. 4 −15 ◦. 9
a 2.112 AU 2.452 AU
e 0.951 0.961
period, the new stream continues at almost exactly the same coordinates (black radiants) to end at α = 365◦ and δ = −04◦ .
i 20 ◦. 5 26 ◦. 2
ω 156 ◦. 8 150 ◦. 0
Ω 322 ◦. 2 309 ◦. 2
Vgeo 37.9 km/s 39.7 km/s
comet of the Machholz group, or possibly a fragment of the main parent body of the Southern δ Aquariid activity. However, a calculation of DSH for each meteor (the mean orbits themselves differ by DSH = 0.26), using the mean orbit of the Southern δ Aquariids as a reference, reveals that DSH is too large for the new stream to be a part of the Southern δ Aquariids, and, therefore, is in fact a previously unknown meteor stream. We presume this went unnoticed because the middle of the stream is located on the 360◦/0◦ boundary, which is easily overlooked in automated algorithms for correlation analysis.
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Figure 4 – Orbits of the Southern δ Aquariids (gray) and the new meteoroid stream (black).
q 0.097 AU 0.087 AU
Conclusions
A possible new meteoroid stream is discovered which may be related to the Southern δ Aquariids. Based on the D-criterion, however, it is clear that these two are different meteoroid streams. Nevertheless, our data reveal that the new stream is continuation of the Southern δ Aquariids, with similar, but not identical, orbits. Further analysis and observations are needed to refine this conclusion. In October 2012, the new stream was registered with the IAU MPC under the name August ι Cetids and code 0505 AIC.
References ˇ and Segon ˇ Andrei´c Z. D. (2010). “The first year of Croatian Meteor Network”. In Kaniansky S. and Zimnikoval P., editors, Proceedings of the Internaˇ tional Meteor Conference, Sachtiˇ cka, Slovakia, 18– 21 September 2008, IMO, pages 16–23.
Figure 5 – Radiants of the Southern δ Aquariids (gray) and the new meteoroid stream (black).
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Discussion
ˇ Segon ˇ Andrei´c Z., D., and Korlevi´c K. (2010). “The second year of Croatian Meteor Network”. In Andrei´c ˇ and Kac J., editors, Proceedings of the InterZ. national Meteor Conference, Poreˇc, Croatia, 24–27 September 2009, IMO, pages 26–30. Southworth R. B. and Hawkins G. S. (1963). “Statistics of meteor streams”. Smithsonian Contr. Astrophys., 7, 261–285.
The comparison of Southern δ Aquariids to the new stream reveals similarities between them. On Figures 4 Vida D. and Novoselnik F. (2011). “Croatian Meteor Network: data reduction and analysis”. In Asher and 5, we see that the activity period of the new stream D. J., Christou A. A., Atreya P., and Barentsen overlaps with the end of the Southern δ Aquariid activG., editors, Proceedings of the International Meity. This may imply that the latter shower has a longer teor Conference, Armagh, Northern Ireland, 16–19 period of activity than previously thought. In this case, September 2010, IMO, pages 96–100. the parent body of the new stream may be another
